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As we said before, arrays can contain any kind of data type, be it `int`, `char`, or anything else. Interestingly, arrays can also store other arrays! An array containing other arrays is known as a multidimensional array. These kinds of arrays are frequently used in mathematical applications that involve matrices and vectors. Similar to its single dimension counterpart, a multidimensional array can be initialized or uninitialized upon its creation. Let’s take a look at the uninitialized version first. The following is a two-dimensional array of integers called `mat` which represents a three-by-four matrix:

``int mat;``

The previous code indicates that the array `mat` contains three elements each of which is an array that contains four integers. To visualize this, consider a row of three lockers, in which each locker contains four sub-lockers that someone can store items in. To illustrate how to create an initialized multidimensional array, we will create a two-by-three multidimensional array called `mat2` composed of random integer values.

``int mat2[] = {{1, 6, 3}, {5, 9, 2}};``

Just like in the single dimension case, the array is initialized by placing elements between `{}` brackets. In this case, the elements inside the outermost brackets are arrays of three elements each. It is important to note that while the two-by-three dimension can be inferred from the right-hand side of the expression, the only dimension that can be omitted is the first (notice the first `[]` is empty); all others must be supplied. The array `mat2`, represents this table: While it is possible to have a theoretically infinite number of dimensions, in practice, dimensions greater than two are very rare. For a two-dimensional matrix, the first dimension represents the number of rows and the second dimension represents the number of columns.

### Instructions

1.

Create a two-dimensional nine-by-nine uninitialized array of integers called `arr`.

2.

Given the following table: Create an initialized two-dimensional array called `matrix` that represents it.